It sure as h-e-double hockey sticks seems like plenty of folks are getting their noises all out of joint over something that is a fairly elementary question. The answer, of course, is that any store owner should give a discount to anyone he wants to. If he wants to give discounts to military guys, fine. If he wants to give it to LEOs, fine. If he wants to give it to members of the money-grubbing NRA (of which I am a member, thank you very much), fine. Ultimately, it's a question of whether he feels that is (a) beneficial to his bottom line and/or (b) is something he should do because of what he thinks some group has done for him or this country.
Personally, I'd give a discount to military guys and gals. Despite what a post somewhere up there ^ might suggest, many folks in the military don't make a lot of money, particularly the younger enlisted kids (a fair number of whom can only support a family with the help of food stamps). In addition to their lavish pay, they get to be deployed to toilet pits of the world on a regular, extended basis. They eat crappy food and sometimes spend extended periods in the field. They often get shot at or targeted with IEDs. Pretty frequently, as a result of the stresses they go through, their marriages disintegrate. And, not too infrequently, they come home in caskets. If a gun shop owner wants to give a discount to them, either because he appreciates their sacrifices or because he appreciates the fact that they have undergone these struggles to serve our nation, I find it hard to see how anyone could have a problem with that. Unless, of course, you only view the world in terms of dollars and cents.
As far as LEOs are concerned, I maybe get a little less worked up. But, I can see similar considerations, and understand why a gun shop owner might feel that the men and women who wear badges should be given a bit of respect . . . and maybe a break on prices.
Underlying all of this, of course, is the whole notion that sometimes doing these things is actually good for business. If you're a merchant who is known to treat soldiers well, it's just possible that other soldiers will shop at your store. It's likely that even a civilian or two might see what you're doing and throw some business your way because they like it. If you give cops a bit of a discount, it's likely they'll let their buddies know, perhaps resulting in more business.
I wouldn't suggest that anyone be required to sell at a discount, nor would I suggest that they ought to cut their profit so deeply as to drive themselves out of business. What I would suggest, though, is that sometimes it's okay to give someone a little bit of a break just because you appreciate what they've done for you and yours.